Commercial polyester adhesives are available which can be used for bonding fabrics and metals. It would be advantageous to be able to broaden the temperature range at which bonds can be made with these adhesives and still allow good bond strengths to be obtained. It would also be advantageous to be able to increase the strength of bonds made with these adhesives on metal substrates. It has now been found that certain low-melting, thermoplastic copolyesters containing small amounts of dimethyl 5-sodiosulfoisophthalate or related difunctional sulfonate metal salts allow the use of a wider bonding temperature range with fabrics and also provide increased bond strengths on metal substrates.
Patents of interest which disclose polyesters and polyesteramides containing sulfonate groups in the form of a metallic salt and at least 15 mol % of at least one glycol). include U.S. Pat. Nos. 4,233,196, 3,734,874 and 3,779,993. In general, these patents disclose compositions derived from a metal sulfonate group attached to an aromatic nucleus wherein the functional groups are hydroxyl, carboxyl, or amino. These polymers are used primarily as water-dispersible sizes for fibers.
U.S. Pat. No. 4,104,262 relates to a water-dispersible polycondensation polyester resin having moieties of at least one polycarboxylic acid and at least one polyvalent alcohol of the terminal hydroxyl groups, said polyester having a molecular weight between 300 and 3,000, a softening point between 30.degree. and 60.degree. C. wherein said polyester additionally contains an amount of 1 to 5 mol percent, based upon the moieties of polycarboxylic acids or polyvalent alcohols, moieties of an alkali metal-sulfo group containing polycarboxylic acid or polyvalent alcohol. U.S. Pat. No. 4,499,262 relates to a process for producing sulfo-modified polyesters using a particular catalyst system. The process comprises the steps of
(a) reacting under polyester forming conditions
(1) a 100 mol % dicarboxylic acid component comprising at least about 85 mol % terephthalic acid or an ester-forming derivative thereof and about 0.1 to about 5.0 mol % of a difunctional sulfo-monomer containing at least one metal sulfonate group attached to an aromatic nucleus, wherein the functional groups are hydroxyalkoxy, carboxyl, or amino, PA1 (2) a 100 mol % glycol component comprising at least about 85 mol % ethylene glycol. PA1 Ar represents the benzene nucleus PA1 X stands for hydrogen, methyl or the group MeO.sub.2 S--CH.sub.2 -- and PA1 n is 1 or 2 PA1 (a) about 0.2-6 mol % of at least one difunctional sulfomonomer containing at least one metal sulfonate group attached to an aromatic nucleus wherein the functional groups are hydroxy or carboxy. PA1 (b) at least one dicarboxcylic acid selected from the group consisting of aliphatic, alicyclic or aromatic dicarboxylic acids having 2-20 carbon atoms, PA1 (c) at least one glycol selected from the group consisting of aliphatic, or alicyclic glycols having 2-12 carbon atoms, PA1 (d) at least one dicarboxylic acid different from (a) or (b), having 2-20 carbon atoms, or at least one glycol different from (a) or (c) having 2-12 carbon atoms,
U.S. Pat. No. 3,634,541 relates to polyester comprising, in addition to the usual dicarboxylic acid moiety and diol moiety, definite amounts of araliphatic sulfonate radicals of the general formula ##STR1## in which Me stands for alkali metal,
in the polymer molecule. The polyesters and the shaped structures made therefrom have a good affinity for basic dyestuffs and the dyeings obtained are very fast to light.